This application relates generally to gas turbine engines and, more particularly, to methods and apparatus for cooling gas turbine engine rotor blades.
At least some known rotor assemblies include at least one row of circumferentially-spaced rotor blades. Each rotor blade includes an airfoil that includes a pressure side, and a suction side connected together at leading and trailing edges. Each airfoil extends radially outward from a rotor blade platform to a tip, and also includes a dovetail that extends radially inward from a shank extending between the platform and the dovetail. The dovetail is used to couple the rotor blade within the rotor assembly to a rotor disk or spool. At least some known rotor blades are hollow such that an internal cooling cavity is defined at least partially by the airfoil, through the platform, the shank, and the dovetail.
During operation, because the airfoil portion of each blade is exposed to higher temperatures than the dovetail portion, temperature gradients may develop at the interface between the airfoil and the platform, and/or between the shank and the platform. Over time, thermal strain generated by such temperature gradients may induce compressive thermal stresses to the blade platform. Moreover, over time, the increased operating temperature of the platform may cause platform oxidation, platform cracking, and/or platform creep deflection, which may shorten the useful life of the rotor blade.
To facilitate reducing the effects of the high temperatures in the platform region, shank cavity air and/or a mixture of blade cooling air and shank cavity air is introduced into a region below the platform region to facilitate cooling the platform. However, in at least some known turbines, the shank cavity air is significantly warmer than the blade cooling air. Moreover, because the platform cooling holes are not accessible to each region of the platform, the cooling air may not be provided uniformly to all regions of the platform to facilitate reducing an operating temperature of the platform region.